Listen Technologies LT-82 User manual

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Installation and Operation

LT-82 Stationary IR Transmitter

LA-140 Stationary IR Radiator

User Manual

®

For further details regarding use, adjustment, or programming of your Listen Technologies products visit

our website at www.listentech.com/support-manuals or contact us at +1.801.233.8992 or 1.800.330.0891.

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Stationary Infrared Table of Contents

Design Guide

Infrared Technology Overview 3

System Overview 5

Designing a System 7

Design Tools 17

LT-82 Stationary IR Transmitter

Specications 23

Block Diagram 24

Quick Reference Page 25

Setup and Operating Instructions 26

Accessories for LT-82 31

LA-140 IR Radiator

Specications 33

Quick Reference Page 34

Setup Instructions 35

LED Indications 36

Mounting your Radiator 38

Accessories for LA-140 58

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Infrared Technology Overview

Infrared or “IR” technology uses infrared light to transmit audio without wires. This type of transmission is

advantageous to RF transmission because it is secure, it is not susceptible to RF interference, and one receiver

can be used for multiple rooms within a facility. The transmitter accepts an audio signal and then frequency

modulates an RF carrier at 2.3, 2.8, 3.3, and/or 3.8MHz. This carrier along with DC power (to power the

radiator) is supplied to the radiator via cables. The carriers are then radiated into the room using IR emitter

diodes. This is the same technology used by the remote control of your TV set. A receiver then receives the

IR light and demodulates the carrier.

1

2 3

4

Audio Source

IR Transmitter

Radiator

Receiver

When designing an IR system it is important to keep the following in mind:

• In open space (when there are no reective surfaces) IR is line of sight. If the receiver cannot “see” light

from the radiator, it will not receive the audio signal. It is important to provide sucient IR coverage

within a facility, so users will not have drop outs of the IR signal. This design guide will help you do this.

• In facilities that have reective and lighter colored surfaces, the IR light will be reected and you can

achieve greater coverage. For example, when emitting in a very large room (like an exhibit hall) you will

notice that you need to point the receiver directly at the radiator to pick up the signal. However, when

the radiator is placed in a smaller room (for example 50 ft

2

/14.6 m

2

square) with white walls you will

experience much better coverage. This is because the IR signal is being reected in many dierent

directions, increasing coverage.

• Listen Technologies systems use higher modulation frequencies that make the system less susceptible

to light interference from uorescent lights and other sources. However, the system is not immune from

interference from sources that create IR light such as sunlight and plasma displays.

• Listen Technologies products are compatible with other manufacturers who use the same modulation

frequencies (2.3, 2.8, 3.3, 3.8 MHz).

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System Overview

There are three main components of any Stationary IR system: the transmitter, radiator (emitter), and receivers.

A single channel system consists of one LT-82 transmitter and one or more radiators. The diagram below shows

such a system with one radiator. The radiator is powered from the power supply at the transmitter. This power

supply can supply enough power for the LT-82 and up to two LA-140 radiators. If you need more than two radia-

tors, you will need more power supplies. This is discussed later in this document. Power is supplied from standard

CAT-5 cable while RF from the transmitter is delivered using 50-ohm RG-58 coaxial cable. The radiator

is supplied with 25 feet (7.6 meters) of CAT-5 and RG-58 coaxial cable.

Single Channel System

LT-82 Stationary IR Transmitter

Mounting hardware for

radiator included with

radiator

RF – RG-58 50 ohm Cable

LR-42 IR Stetho Receiver

LR-44 IR Lanyard Receiver

Power – CAT-5 Cable

LA-140 IR Radiator

IR

1

2 3

4

1

2 3

4

1

2 3

4

1

2 3

4

LT-82 Transmitter

LA-140 Radiator

LR-42 LR-44

1

2 3

4

1

2 3

4

LR-4200-IR Intelligent

DSP IR Receiver

LR-5200-IR Advanced

Intelligent DSP IR Receiver

LT-82 Stationary IR Transmitter

Mounting hardware for

radiator included with

radiator

RF – RG-58 50 ohm Cable

LR-42 IR Stetho Receiver

LR-44 IR Lanyard Receiver

Power – CAT-5 Cable

LA-140 IR Radiator

IR

1

2 3

4

1

2 3

4

LR-4200-IR Intelligent

DSP IR Receiver

LR-5200-IR Advanced

Intelligent DSP IR Receiver

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System Overview

A multiple channel system consists of two to four LT-82 transmitters and one or more radiators. The diagram

below shows such a system with two radiators. The radiators are powered from the power supply from the

rst transmitter. This power supply can supply enough power for the LT-82 and two LA-140 radiators. If you

need more than two radiators, you can use the power from the other transmitters. In this example, the four

transmitter power supplies can supply enough power for up to eight LA-140 radiators. This is discussed later

in this document. Power is supplied from standard CAT-5 cable while RF from the transmitter is delivered

using 50-ohm RG-58 coaxial cable. Each radiator is supplied with 25 feet (7.6 meters) of CAT-5 and RG-58

coaxial cable.

Multiple Channel System

Up to four LT-82 transmitters can

be daisy chained together

(using RG-58 cable) to create

a multi-channel system

LA -89 RG-58 Multi-carrier

Interconnection Cable

(included)

RF – RG-58 50 ohm Cable

Up to 100 LA-140 radiators can be daisy chained

together (using RG-58 cable) to provide

suﬃcient IR power for most applications

LR-42 IR Stetho Receiver

LR-44 IR Lanyard Receiver

Radiator Power: Radiators can be

powered from the LT-82 (up to two

radiators) or an additional power supply

(LA-205) can power up to two radiators

Radiator RF: RF from the last LT-82 must be

daisy chained from radiator to radiator

Power – CAT-5 Cable

LA-140 IR Radiator

IR

LT-82 Stationary IR Transmitter

1

2 3

4

1

2 3

4

LR-4200-IR Intelligent

DSP IR Receiver

LR-5200-IR Advanced

Intelligent DSP IR Receiver

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System Overview

Each LT-82 transmitter used can power up to two LA-140 radiators. If you design a system that requires more

radiators than the transmitters can power, you need to order additional LA-205 power supplies. Each LA-205

can power up to two LA-140 Radiators.

Key Concepts of Designing a Stationary IR System

1

Each LT-82 transmitter used can power two LA-140 radiators

Up to four LT-82 transmitters can be interconnected to create up to a four channel system. For the system,

there are two RF outputs provided for connection to the radiators. Each of these two outputs is referred to as

the “Radiator Daisy Chain.” RG-58 coaxial cable is used to interconnect the RF in the radiator daisy chain. You

can connect as many radiators in the daisy chain as you need.

2

Up to four LT-82 transmitters can be interconnected to create up to a four

channel system

Each radiator requires one RF (RG-58 coax) connection and one power (CAT-5) connection. The RF

connection can come from a transmitter or from another radiator. The power connection can come from

either a transmitter, a radiator or from a power supply (as long as you don’t exceed the capacity).

3

Each radiator requires one RF (RG-58 coax) connection and one power

(CAT-5) connection

To make it easy for you to design, specify and install a system, Listen Technologies has provided mounting

hardware for most mounting situations including wall, ceiling, corner, desk, tripod and mic stands. To double

the radiation power you can vertically or horizontally mount two radiators together using the LA-342 dual

radiator mounting brackets. This includes coaxial RF and CAT-5 power cables.

4

Listen Technologies has provided mounting hardware for most LA-140

mounting situations

Due to the higher modulation frequencies, it is possible that the RF signal arrives to dierent radiators at

dierent times. This delay can cause the IR carriers to add “out of phase” and cause the signal to drop out.

To solve this problem, Listen Technologies has provided a delay compensation adjustment on each radiator.

This design guide will help you calculate the setting for this adjustment.

5

It is possible that the RF signal arrives to dierent radiators at dierent times

As the number of channels increases, the eective radiated coverage declines. For example, a two channel

system will have half the coverage of a single channel system. If is important to increase the number of

radiators for multiple channel systems.

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As the number of channels increases, the eective radiated coverage declines

The coverage patterns provided by Listen Technologies provide coverage of the system assuming no reection.

In addition, the radiator has been under-rated to account for system degradation as the IR emitting LEDs age

over time. It is important to design the system based on these coverage patterns and not by trial and error. The

reason for this is that the coverage pattern will be stronger when the radiator is new. A system that has adequate

coverage today may not have adequate coverage in the future if not designed according to the specied coverage

patterns of the radiator.

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The coverage patterns provide coverage of the system assuming no reection

CAT-5 power cable should never exceed 250 feet when powering two (2) LA-140’s from an LT-82 or 700 feet

when powering one (1) LA-140 from an LT-82.

8

The maximum length of CAT-5 power cable

NOTE: Adding additional transmitters will decrease radiator coverage.

Coaxial RF signal cable should never exceed 1000 feet from the source transmitter.

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The maximum length of coaxial RF cable

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Up to four LT-82 transmitters can be interconnected to create up to a four

channel system

Each radiator requires one RF (RG-58 coax) connection and one power

(CAT-5) connection

Listen Technologies has provided mounting hardware for most LA-140

mounting situations

It is possible that the RF signal arrives to dierent radiators at dierent times

As the number of channels increases, the eective radiated coverage declines

The coverage patterns provide coverage of the system assuming no reection

The maximum length of CAT-5 power cable

The maximum length of coaxial RF cable

Designing a System

You will need to order one LT-82 transmitter for each audio channel. The Listen system can deliver

up to four audio channels simultaneously.

1

Determine the number of audio channels

You should either measure the room or use the architect’s plans to obtain this information.

2

Determine the room size and shape

Complete the room layout worksheet found in the nal section of this guide placing the location of the

transmitters, power supplies and radiators using the worksheet key. The following factors will determine

the coverage of the room.

3

Complete the room layout worksheet

3A

Except in small rooms it is recommended that at least two radiators be used to ensure good coverage and

minimal shading. Listen Technologies radiators (when used with Listen Technologies ’ LR-42 and LR-44

receivers) will cover approximately 10,000 ft

2

(929 m

2

) for one channel as indicated in the diagram below

(note the coverage decreases as the number of channels goes up). For two channels, one radiator will

cover 5,000 ft

2

(465 m

2

) and for four channels, one radiator will cover 2,500 ft

2

(232 m

2

). When using

LR-4200-IR/LR-5200-IR receivers, the approximate line-of-sight coverage increases to 40,000 ft

2

(3716 m2)

for one channel.

Number of radiators and location

You should use the above coverage pattern to determine coverage of each radiator in your system, not by trial

and error. The radiator will be stronger when new and therefore is under-rated by 40 percent and the coverage

pattern above accounts for this. 40 percent degradation will occur after approximately 8,000 operating hours.

10

0

30

20

50

40

50

20

30

10

20 30 40 50 60 70 80 90 100 110 120 130 140 150

1 TX2 TX4 TX

Horizontal Plane Footprint Pattern (feet)

Coverage

pattern shown

in feet

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Designing a System

Horizontal Polar Pattern

Vertical Polar Pattern

Single Channel System

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Designing a System

In this example a total of four radiators, one in each corner, ensures good coverage at all

locations and orientations.

Except in small rooms, it is recommended that at least two radiators are used to prevent

shading of the IR signal.

It is a good idea to provide over-lapping coverage (like in a sprinkling system) of the signal whenever possible to ensure that

the signal does not have drop outs. In addition, you should provide special radiator coverage for shaded areas such as under

a balcony or in the front of a room where the front mounted radiators do not provide enough coverage.

The following diagrams illustrate these concepts.

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Designing a System

If there is an area within a room (such as under a balcony) that is

shielded from the main radiation pattern, you will need to provide

additional radiator(s) to cover this area.

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Designing a System

To double the radiator power, it is possible to vertically or horizontally mount two radiators together using the

LA-342 Dual Radiator Mounting Bracket (sold separately). This is highly recommended in larger rooms.

RAD 1

RAD 2

3B

It is critical to mount the radiators at the proper height. If the radiator is mounted too low, the coverage pattern

will be too small to provide sucient long throw coverage. If the radiator is mounted too high the required angle

of the radiator will cause the radiation pattern to be compromised. The best height of the radiator is about 16 ft

2

(5 m

2

) from the oor.

Height of Radiators

3C

The mounting system for Listen Technologies LA-140 radiators allow you to mount the radiator in 15 degree

increments. The best angle depends on the shape of the room and the orientation of the radiator to the seats

within the room. In general, mounting angles of 15 and 30 degrees provide the best coverage.

Radiator Mounting Angle

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Designing a System

Determine the number of radiators required based on the size and shape of the room. Based on step two, it is

recommended that you draw the room out indicating the location of each radiator in the room and cable runs from

the transmitter(s) and power supplies (if any) to the radiator. We have provided the room layout worksheet for you

to do this towards the back of this design guide. See example below:

4

Determine the number of radiators required

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Complete the system layout worksheet for Power and RF cable lengths, delay compensation, required number

of power supplies, and height and angle of radiators. Refer to the system layout worksheet example below.

5

Complete the system layout worksheet

Designing a System

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Designing a System

5A

Cross out the LT-82 transmitters not required in your system.

Cross out the LT-82 transmitters

5B

Determine how many radiators will be used on each radiator daisy chain by reviewing the room layout

worksheet. Cross out the unused radiators on the system layout worksheet.

Determine how many radiators will be used

5C

Write in the coaxial RF cable lengths for each radiator used in the spaces provided. Review your room layout

worksheet for this information.

Write in the coaxial RF cable lengths for each radiator

5D

Draw a connecting line from the power supply output of the LT-82 transmitter(s) and the LA-205 power

supplies to each of the radiators. Keep in mind that each transmitter and power supply can power up to two

LA-140 radiators.

Draw a connecting line from the power supply output

5E

Cross out the unused power supplies.

Cross out the unused power supplies

5F

Write in the CAT-5 power supply cable lengths for each radiator used in the spaces provided. Review your

room layout worksheet for this information.

Write in the CAT-5 power supply cable lengths

5G

Now determine the delay compensation for each radiator using the Delay Compensation Calculator located

in the back of this design guide. The correct setting of the delay compensation is necessary only in systems

where there is overlap in coverage between two or more radiators. Write the delay setting on the System

Layout Worksheet. The delay setting for each radiator is determined using the calculator and as follows:

Determine the delay compensation for each radiator

Determine which radiator is the furthest from the transmitter on one of the two daisy chains.

Calculate the distance from the furthest radiator to the transmitter and record it in the rst

column of the delay compensation calculator. See example below.

Distance of Furthest Radiator (DFR)

1

For each radiator, determine the overall distance from the transmitter to the radiator.

Record the value of each radiator in the RDT column. See example below.

Radiator Distance from Transmitter (RDT)

2

Determine and record the propagation delay of the coaxial cable being used. For Listen

coaxial cable the delay is 1.54 ns/ft or 5.05 ns/m. This information can be obtained from the

specication sheets supplied by the cable manufacturer.

Cable Delay (CD)

3

Now calculate the delay setting for each radiator using the Delay Compensation

Calculator. The calculator uses the following formula to determine the delay setting of each

radiator:

Calculate the delay setting for each radiator

4

Delay Setting = (DFR – RDT) x CD / 25

NOTE: If your calculations suggest a delay setting greater than nine, please

contact Listen Technologies tech support for more information.

1.801.233.8992

[email protected]

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Designing a System

Complete the system materials worksheet that determines the quantity of each part number required

for your system. Use the Room and System Layout Worksheets to ll in this form found in the last

section of this guide.

6

Complete the system materials worksheet

6A

Fill in the number of transmitters required. Each transmitter includes a short piece (15 inches) of RG-58

coaxial RF cable for multiple channel installation interconnections. You do not need to order this cable.

Transmitters

6B

Fill in the number of rack mounting kits required. One rack mount kit can mount two LT-82 transmitters.

Transmitter Rack Mounting

6C

Fill in the number of each type of radiator required. Each radiator comes with mounting brackets for most

types of installation. In addition, the radiator comes with 25 ft (7.6 m) of coaxial RF and CAT-5 power cables.

Radiators

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Designing a System

6D

Since the radiator comes with most radiator mounting options, there are only two additional choices.

Radiator Mounting Options

The LA-342 dual radiator mounting bracket allows you to mount two radiators together

(vertically or horizontally). This includes short lengths of coaxial RF and CAT-5 power cables.

Dual radiator mounting

1

The LA-337 is a oor stand for portable applications.

Floor stand

2

6E

Fill in the number and type of LA-205 power supplies required (if any).

Radiator Power Supplies

6E

From the System Layout Worksheet, insert the cable lengths for the preassembled coaxial RF cables (LA-391) and

CAT-5 power cables (LA-393).

Cables

6F

For US customers, Listen Technologies oers the ADA Compliance Signage Kit (LA-304). This aids in

complying with US ADA regulations.

Other Accessories

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KEY

LT-82

LA-140

RG-58

CAT-5

KEY

LT-82

LA-140

RG-58

CAT-5

Room Layout Worksheet

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System Layout Worksheet

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